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Recovery of excreted n-butanol from genetically engineered cyanobacteria cultures: Process modelling to quantify energy and economic costs of different separation technologies

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journal contribution
posted on 03.12.2018, 14:57 by Jonathan WagnerJonathan Wagner, Daniel Lee-Lane, Mark Monaghan, Mahdi Sharifzadeh, Klaus Hellgardt
The photoautotrophic production of excreted biofuels from genetically engineered cyanobacteria and microalgae represents a new and promising alternative to conventional algal fuel technologies. N-butanol is a particularly promising fuel product, as it can be directly used in petroleum engines, and has been successfully expressed in species of Synechococcus elongates 7942 and Synechocystis sp. PCC 6803. However, the high energy requirements of recovering butanol from dilute mixtures can easily outweigh the energy content of the fuel and must be carefully assessed and optimized. Consequently, the recovery of butanol was modelled using four of the most promising butanol separation technologies (distillation, gas stripping, pervaporation and ionic liquid extraction) to calculate the minimum butanol culture concentrations required to render the process energy-positive. With a breakeven concentration of only 3.7 g L -1 , ionic liquid extraction proved much more efficient than the distillation base-case scenario (9.3 g L -1 ), whilst neither pervaporation (10.3 g L -1 ) nor gas stripping (16.9 g L -1 ) could compete on an energy basis with distillation. Despite this, due to the high costs of the ionic liquid solvent, the lowest capital costs are obtained for distillation (pilot plant scale, butanol culture concentrations of 10 g L -1 ), whilst pervaporation carries the lowest utility costs, as a result of its low electrical energy demand. Although currently achieved maximum n-butanol culture concentrations are significantly below the calculated break-even values for all four technologies, the present work provides an important threshold for future strain development. Moreover, the recovery of side-products from purged biomass could help to reduce the costs associated with biofuel production.

Funding

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 640720

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Chemical Engineering

Published in

Algal Research

Volume

37

Pages

92 - 102

Citation

WAGNER, J.L. ... et al., 2019. Recovery of excreted n-butanol from genetically engineered cyanobacteria cultures: Process modelling to quantify energy and economic costs of different separation technologies. Algal Research, 37, pp. 92-102.

Publisher

© Elsevier

Version

AM (Accepted Manuscript)

Publisher statement

This paper was accepted for publication in the journal Algal Research and the definitive published version is available at https://doi.org/10.1016/j.algal.2018.11.008.

Acceptance date

22/11/2018

Publication date

2018-11-30

ISSN

2211-9264

Language

en